According to a recent presentation relating to the Microsoft and Yahoo! Search Alliance, August/September may see the full rollout of Bing powered Yahoo! search results.

If you’re not up to speed on the deal between Yahoo! and Microsoft, the presentation covers the history to date, plus where things are at now.

For some merchants, this is incredibly good news, for others, it will be a tragedy.

If your web site ranks highly on Bing, but not on Yahoo at the moment, then you’ll most likely see a big jump in traffic from Yahoo! once this happens. If the reverse applies, it’s time to get cracking on Bing SEO.

You may even see erratic peaks and troughs from Yahoo depending on your situation throughout June and July while they run some live testing with a set of users.

This Bing-Yahoo alliance is a very big deal.

While Google rules the roost in the world of search (65.1% US market share in May 2010), according to the latest survey from The Nielsen Company, Yahoo currently has 13.8% US market share and Bing, 13%. Once this change occurs, Bing will effectively have close to 27% market share; assuming of course Yahoo! users like what they see and there’s no mass exodus to Google. Most Yahoo users won’t know the difference and Bing results are pretty good generally, so a big switch to Google is unlikely.

If you have a buddy in online business who relies heavily on Yahoo!, be a real pal and warn them about this upcoming change and what it means. New fortunes will be made once this transition occurs, but some online merchants who haven’t been keeping their fingers on the Microsoft and Yahoo! search alliance pulse could go to the wall.